This invention relates to mechanism for varying the compression ratio of four cycle engines. The mechanism is designed to adjust the position of the engine crankshaft rotational axis toward or away from the combustion chamber, to thereby vary the clearance volumes when the pistons are in their top dead center positions.
U.S. Pat. No. 2,433,639 to Woodruff et al and U.S. Pat. No. 2,589,958 to Petit disclose engines wherein the main bearings for the crankshaft are carried on cradle structures that can be swung around pivot mechanisms spaced laterally from the crankshaft bearings. The present invention is an improvement on the constructions disclosed in those patents.
General objects of the invention are to provide a crankshaft-adjusting mechanism wherein:
1. The output shaft centerline is fixed. There is no need for a universal joint between the engine output shaft and the associated transmission.
2. The mechanism achieves a speed change (between the engine drive shaft and transmission input).
3. The mechanism operates without reliance on elongated lever arms subject to distortion or breakage under high load forces imposed on/by the crankshaft.
4. The mechanism includes a stroke reduction connection between the adjustment power means and crankshaft support element, whereby small incremental changes in crankshaft position can be realized.
5. The mechanism is controllable electrically via electronic signals generated by microprocessor equipment already used to program engine operations.
6. The mechanism can be incorporated into existing engine designs with relatively minor changes in engine construction.
7. The mechanism does not appreciably increase the overall size of the engine.
8. The mechanism is relatively inexpensive.